Peruvian Ceviche

Name: Peruvian Ceviche
Ingredients: 2/3 cup fresh lime juice; 2 garlic cloves, smashed; 1 tablespoon (packed) chopped fresh cilantro leaves; 1/2 ají limo or habanero chile, seeded; 1/2 small red onion, chopped; 1/2 cup bottled clam juice (optional); Kosher salt; 1 small sweet potato (about 8 ounces); 1 ear of corn, husked; 1 ají limo or habanero chile, seeded, halved lengthwise; 1 pound fluke, flounder, or sole, cut into 1/2 cubes; 1 small red onion, quartered and thinly sliced, divided; Cilantro leaves; Ingredient info: Ají limo chiles are sold at Latin markets; look for habanero chiles at some supermarkets and at Latin markets.